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ER/MR유체를 이용한 기기 제어 시스템.
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The electrorheology (ER) 유체
Definition: 전기유변유체는 일반적으로 절연성의 유체에 분극성이 강한
미립자가 분산된 현탁액(suspension)으로서 외부에서 강한 전기장이인가되면 그 유변학적 역학적 특성이 변하는 유체.
ER유체는 1947년 Willis Winslow 비전도성 오일 내의 절연입자들이 부과된 전기장에 의존하여 반응하는 현상을 발견
-> 외부에서 가해진 전기장에 의하여 입자들이 전기장 방향으로 정렬되어 사슬모양 구조를 형성하며 전기장의 크기에따리 유체의 점도가 큰 폭으로 변하는 현상을 관측
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1. Size: Electrorheological (ER) fluids are suspensions of extremely
fine non-conducting particles (up to 50 micrometer diameter) in an
electrically insulating fluid.
2. Effect: The apparent viscosity of these fluids changes reversibly
by an order of up to 100,000 in response to an electric field. For
example, a typical ER fluid can go from the consistency of a liquid
to that of a gel, and back, with response times on the order of
millisecond.
3. The effect is sometimes called the Winslow effect.
Composition of ER fluid
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Applications:
(1) Car suspension systems that automatically adjust to road
conditions
(2) Helicopter damping struts
(3) Hydraulic actuator systems
(4) Aircraft landing gear
(5) Robotic systems
Viscosity f(E2)
Electrodes
Medium
Particle
Reversible
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Newtonian Fluid:
The concept was first deduced by Isaac Newton and is directly
analogous to Hooke's law for a solid. All gases are newtonian,
as are most common liquids such as water.
Where τ is the shear stress exerted by the fluid
μ is the fluid viscosity - a constant of proportionality [Pa·s]
is the velocity gradient perpendicular to the
direction of shear [s−1]
A fluid sheared between two plates.
The resulting strain rate equals V/H
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Non-newtonian Fluid
ER fluid
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Basic Principle of ER fluid
Electric constant:
The Coulomb Force Law states that any two charged particles
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Magnetorheology(MR) Fluid
(1) Silicone base coupled with a suspension of magnetically
soft particles
(2) When an applied magnetic field aligns the metal particles
into fibrous structures
(3) Rheological behavior changes from Newtonian to Bingham
plastic
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Jacob Rabinow (right)
and colleagues
demonstrated MR
fluid in a 1940s-era
National Bureau of
Standards photo.
Jacob Rabinow invented
MR fluid while he was
at the National Bureau of
Standards in the 1940s.
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Operation modes of ER/MR fluid
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MR fluid damper/lock working principle
14www.lord.com/Portals
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Prosthetic Joint
www.lord.com
Applications
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MR Shock Absorber
<Vehicle MR Shock Absorber>
www.ssslab.com
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Vehicle Suspension Dampers
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MR Transmission Clutches
The MR sponge clutch may be used to
provide launch control of an automobile
thereby achieving smooth vehicle launch.
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ER damper
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ER damper의 피스톤 속도와 댐핑력
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MR Impact Damper
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MR Engine Mount
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24ER 엔진마운트 특성
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Audi's new R8 road-going sports car
Called Audi Magnetic Ride this innovative technology uses magneto-
rheological fluid-filled dampers to provide continuously variable real-
time suspension damping control.www.fourtitude.com
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Linear Electromagnetic Suspension
(invented by Bose)
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VEHICLE DYNAMICS:
…Apart from new springs and a stiffer rear anti-roll bar, the car also
features a second generation magneto-rheological suspension control
system (SCM2)….
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It is estimated that a
damper of 200kg can
resist a force of
20000N of force.
lh4.ggpht.com
(1) Earth quakes
and vibrations
(2) Temperature
stresses
(3) Corrosion of
reinforcement
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Yokohama Landmark Tower
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Passive Control
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A structure which can adapt to the changing environmental
conditions is called SMART.
lh4.ggpht.com
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Micro-gripper
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<ECF응용 마이크로 모터>
ECF(electro-conjugate fluids)
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<비대칭노면 시험중의 차량 운동 비교>
<ER-ABS시스템의 개략도>
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기존의 동력조향장치(Power Steering,
PS)은 고속 주행 시 조향 안전성이 나빠지는 단점을 가진다.
이러한 단점을보안한 것이 속도 감응 동력 조향 장치(Electronically Controlled Power
Steering, ECPS)이다.
Electronically Controlled Power Steering, ECPS
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An advantage is that an ER device can control considerably more
mechanical power than the electrical power used to control the effect, i.e.
it can act as a power amplifier.
A problem is that ER fluids are suspensions, hence in time they tend to
settle out, so advanced ER fluids tackle this problem by means such as
matching the densities of the solid and liquid components, or by using
nanoparticles, which brings ER fluids into line with the development of
MR fluid.
Problems and advantage
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Another problem is that the breakdown voltage of air is ~ 3 kV/mm,
which is near the electric field needed for ER devices to operate.
Other main advantage is the speed of response, there are few other
effects able to control such large amounts of mechanical or hydraulic
power so rapidly
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Design of MR fluid system
